1. Field of the Invention
This invention relates generally to a brushless generator, and more particularly to a brushless generator of a self-excited synchronous type; the brushless generator being a small-sized generator of a rotating-field type having a stator with the stator magnetic poles thereof integrally formed with yokes, in which slots are provided on the stator magnetic poles, and exciting windings are wound on the slots to generate voltages having different phases with that produced in the main generating winding to eliminate brushes, and electric power is generated by selecting the number of poles of the main generating winding wound on the stator and the number of poles of the exciting windings, selecting the construction of the rotator, and by forming a return path in the exciting winding.
2. Description of the Prior Art
A generator of a type in which the alternating voltage induced in a field winding is rectified by a diode to use as a field current for the field winding is heretofore known as a brushless single-phase generator having a simple construction and excellent characteristics. A brushless 2-pole, 3-phase generator as shown in FIG. 15 has also been developed based on the basic principle of the abovementioned type of generator. In FIG. 15, reference numeral 1 refers to a stator; 2 to a rotor; 3 to a 2-pole, 3-phase main generating winding; 4 to a single-phase, 4-pole exciting winding; 5 to a d-c power source; 6-1a through 6-1d to field cores; 6-2a through 6-2d to salient poles; 7a through 7d to field windings; and 8 to a diode, respectively.
In the example shown in FIG. 15, the field windings 7a through 7d are wound on the field cores 6-1a through 6-1d of a 4-pole construction provided on the rotor 2. The diode 8 is connected to each of the field windings 7a through 7d so that the field cores 6-1a through 6-1d are magnetized as magnetic fields of S, S, N and N are sequentially generated in the salient poles 6-2a through 6-2d. That is, when the rotor 2 rotates in the embodiment shown in FIG. 15, the static magnetic field of the exciting windings 4 causes a field current to flow in the direction shown by arrows in the figure in the field windings 7a through 7d to magnetize the field cores 6-1a through 6-1d. This produces an apparently 2-pole magnetic field, thus yielding a 3-phase alternating output on the 2-pole, 3-phase main generating winding 3.
On the other hand, a generator of a self-excited, rotating-field type (concentrated winding type), as shown in FIG. 16, is heretofore known as a synchronous generator. This type of generator has been widely used because of its simple construction. In FIG. 16, numeral 9 refers to a stator; 10 to a rotor; 11 to a stator magnetic pole; 12 to a yoke; 13 to a main generating winding; 14 to an exciting winding; 15 to an automatic voltage regulator (AVR); 16 to a brush slip ring; 17 to a field winding; 18 to a rotor core; and 19 to a salient pole, respectively.
In the example shown in FIG. 16, as the rotor is rotated, a voltage proportional to the intensity of the magnetic field intersecting the exciting winding 14 is induced. Along with this, a current is supplied to the field winding 17 via the AVR 15 to magnetize the rotor core 18, producing an alternating output in the 2-pole main generating winding 13.
In the example shown in FIG. 16, it is difficult to eliminate the brush slip ring 16 because of the need to supply the current generated in the exciting winding 14 on the stator to the field winding 17 wound on the rotor.
In addition, the brushless generator of the conventional type shown in FIG. 15 is constructed so that an exciting current for the exciting windings 4 is supplied by the external d-c power source 5. This entails the need for an external d-c power source.
When used with a single-phase load, this type of generator, which has a low load compensation, tends to involve an increase in voltage drop when the load current is increased.